Cuttings injection and annulus remediation systems for wellheads

ABSTRACT

A wellhead assembly has an inner wellhead that lands in an outer wellhead, the inner wellhead having first and second internal passages. Each passage has an upper opening at the outer surface of the inner housing and a lower opening at the inner surface. An external shoulder of a casing hanger lands on an internal shoulder of the inner housing, the lower opening of the first passage being below the internal shoulder, the lower opening of the second passage being above the internal shoulder. The casing hanger has a substantially-vertical passage located in its sidewall, an upper port registering with the lower opening of the second passage, a lower port being located below the external shoulder for communicating with the annulus. Valve assemblies at the upper openings control the flow of heavy fluid injected into a casing annulus through the second passage and of cuttings injected into the annulus through the first passage.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Benefit is herein claimed of the filing date under 35 USC §119and/or §120 and CFR 1.78 to U.S. Provisional Patent Application SerialNo. 60/271,016, filed on Feb. 23, 2001, entitled “Cuttings Injection andAnnulus Remediation Systems for Wellheads.”

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention generally relates to wellhead and casingassemblies for oil production and particularly relates to an assemblyproviding for cuttings injection and annulus remediation.

[0004] 2. Description of the Prior Art

[0005] When a subsea well is drilled, cuttings, which are small chipsand pieces of various earth formations, will be circulated upward in thedrilling mud to the drilling vessel. These cuttings are separated fromthe drilling mud and the drilling mud is pumped back into the well,maintaining continuous circulation while drilling. The cuttings in thepast have been dumped back into the sea.

[0006] While such practice is acceptable for use with water baseddrilling muds, oil based drilling muds have advantages in some earthformations. The cuttings would be contaminated with the oil, which wouldresult in pollution if dumped back into the sea. As a result,environmental regulations now prohibit the dumping into the sea cuttingsof produced with oil based drilling mud. There have been variousproposals to dispose of the oil base cuttings. One proposal is to injectthe cuttings back into a well. The well could be the well that is beingdrilled, or the well could be an adjacent subsea well. Various proposalsin patents suggest pumping the cuttings down an annulus between two setsof casing into an annular space in the well that has a porous formation.The cuttings would be ground up into a slurry and injected into theporous earth formation. Subsequently, the well receiving the injectedcuttings would be completed into a production well.

[0007] U.S. Pat. No. 5,085,277, Feb. 4, 1992, Hans P. Hopper, showsequipment for injecting cuttings into an annulus surrounding casing. Theequipment utilizes piping through a template or guide base and throughports in specially constructed inner and outer wellhead housings. Whilefeasible, the method taught in that patent requires extensivemodification to conventional subsea structure.

[0008] Two patents provide for alternative devices for injectingcuttings. U.S. Pat. No. 5,339,912 to Hosie, et al., discloses a systemhaving an injection adapter that removably mounts in an upper portion ofa wellhead housing for injecting cuttings into the casing annulus. U.S.Pat. No. 5,662,169 to Hosie is for a wellhead system with a stab movableinto engagement with the wellhead. The stab moves a flapper valve tocommunicate with the casing annulus for injection of a cuttings slurry.

[0009] Another problem encountered in wells is that of annular pressurecontrol. In the annulus between different casing sizes, pressure maydevelop due to leaks between strings of casing. Previously, to controlthe pressure, a relatively heavy liquid is pumped into the annulus atthe upper end of the well. The heavy liquid migrates slowly downward,displacing lighter liquid. This technique does not always work. U.S.Pat. No. 5,927,405 to Monjure, et al. discloses a system for lowering aflexible hose into the annulus for injecting a heavy fluid at a lowerportion of the annulus.

[0010] There is a need for a wellhead assembly that provides for bothcuttings injection and annulus remediation functions, eliminating theneed for running separate tools or wellhead assemblies.

SUMMARY OF THE INVENTION

[0011] A wellhead assembly has an inner wellhead that lands in an outerwellhead, the inner wellhead having first and second internal passages.Each passage has an upper opening at the outer surface of the innerhousing and a lower opening at the inner surface of the inner housing.An external shoulder of a casing hanger lands on an internal shoulder ofthe inner wellhead housing, the lower opening of the first passage beingbelow the shoulder, the lower opening of the second passage being abovethe shoulder. The casing hanger has a substantially-vertical innerpassage located in its sidewall, an upper port registering with thelower opening of the second passage, and a lower port located below theshoulder for communicating with an annulus formed between strings ofcasing. A conduit extends from the lower port into the annulus forconducting fluid from the inner passage to a lower portion of theannulus. Valve assemblies are located at the upper openings forcontrolling control fluid flow through the first and second passages.

[0012] To inject fluid for annulus remediation, A heavy fluid isinjected into the annulus through the second passage, the fluid enteringthe inner passage of the casing hanger and traveling downward throughthe conduit. Lighter fluid is displaced and flows upward out of theannulus through the first passage. A slurry of cuttings can be injectedinto the annulus through the first passage to flow downward in theannulus and into a porous formation below the lower end of the outerstring of casing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The novel features believed to be characteristic of the inventionare set forth in the appended claims. The invention itself however, aswell as a preferred mode of use, further objects and advantages thereof,will best be understood by reference to the following detaileddescription of an illustrative embodiment when read in conjunction withthe accompanying drawings, wherein:

[0014]FIG. 1 is a cross-sectional view of a wellhead assembly havingcuttings-injection and annulus-remediation systems and constructed inaccordance with the present invention, the flow of fluid being shown asduring annulus remediation;

[0015]FIG. 2 is a cross-sectional view of the wellhead assembly of FIG.1, the wellhead assembly being constructed in accordance with thepresent invention, the flow of fluid being shown as during cuttingsinjection; and

[0016]FIG. 3 is a cross-sectional view of a tubing hanger constructed inaccordance with the present invention and having a seat protectorinstalled therein.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIGS. 1 through 3 show a wellhead and casing assembly having bothcuttings-injection and annulus-remediation systems. Theannulus-remediation system is used to inject heavy fluids when needed toprevent leakage of fluids into the annulus located between adjacentstrings of casing. The cuttings-injection system is used to inject aslurry of cuttings from the drilling of a nearby well into the annulus.These cuttings are injected into the annulus to permanently and safelydispose of the cuttings.

[0018] Referring to FIGS. 1 and 2, an outer wellhead housing 11 is alarge tubular member having a bore 13 located on a vertical axis. Aconductor pipe 15 is secured to the lower end of outer wellhead housing11. Inner wellhead housing 17 is a large tubular member that has a bore19 on a vertical axis and fits securely into bore 13 of outer wellheadhousing 11. The upper end of inner wellhead housing 17 protrudes aboveouter wellhead housing 11, and a string of outer casing 21 is secured tothe lower end of inner wellhead housing 17. Inner wellhead housing 17has an internal shoulder 23 located in bore 19 for supporting a stringof inner casing 25, casing 25 being supported by a casing hanger 26having a mating external shoulder 27, casing 25 having a vertical bore29. The two strings of casing 21, 25 define an annulus 31. At a depthbelow where outer casing 21 terminates, the outer surface of annulus 31is defined by the wellbore at a porous formation 32. For more detail onthe assembly and installation of wellhead housings, see, for example,U.S. Pat. No. 5,662,169.

[0019] Inner wellhead housing 17 has a passage 33 through its sidewallfor injecting remediation fluids and a passage 35 for injectingcuttings. Each passage 33, 35 has an upper opening 37, 39, respectively,on the external surface of inner wellhead housing 17 that is locatedabove outer wellhead housing 11. Annulus-remediation passage 33 has anupper portion 40 beginning at upper opening 37 and leading to a verticalportion 42 running downward within the sidewall of inner wellheadhousing 17. Vertical portion 42 leads to lower portion 45 which isangled toward bore 19. Passage 33 terminates in a lower opening 49 inbore 19 of inner wellhead housing 17 that is located above shoulder 23.Likewise, cuttings-injection passage 35 has an upper portion 41 thatbegins at upper opening 39 and extends to vertical portion 43. Verticalportion 43 extends downward in the sidewall to lower portion 47, whichis angled towards bore 19 and terminates at lower opening 51. Loweropening 51 is also located in bore 19 of inner wellhead housing 17, butopening 51 is located below shoulder 23 and communicates passage 35 withannulus 31. Each upper opening 37, 39 has a valve assembly 53, 55,respectively, for controlling access to upper opening 37, 39.

[0020] Casing hanger 26 has an internal passage 57 with an upper opening59 for communicating with lower opening 49 of remediation passage 33 ininner wellhead housing 17. Upper opening 59 is located above shoulder 27and registers with lower opening 49 when casing hanger 26 is installedwithin inner wellhead housing 17. Seals 61 are positioned above andbelow openings 49, 59 to prevent leakage of remediation fluid from theinterface of openings 49, 59 and to prevent contaminants from enteringpassages 33, 57. Upper portion 62 of passage 57 is angled toward bore19, leading to a vertical lower portion 63 terminating in a loweropening 65. Lower opening 65 has a connector for attaching a conduit 67deployed within annulus 31 and below passage 57. In the preferredembodiment, conduit 67 is a tube terminating in a check orpressure-relief valve 69. Alternatively, conduit 67 may terminate with aburst disk or other cap for retaining pressure within conduit 67.Conduit 67 may extend for thousands of feet downhole, though the lowerend of conduit 67 will be above the level of cement in annulus 31.

[0021] Referring now to FIG. 3, a seat protector 71 is inserted intobore 19 of inner wellhead housing 17 after housing 17 is installed inouter wellhead housing 11 and before drilling is continued. Seatprotector 71 is a tubular sleeve having an outer diameter which isslightly less than the inner diameter of bore 19 above shoulder 23. Thelower end of protector 71 has a mating shoulder 73 for engaging shoulder23 to support protector 71. Seals 75 are located on the external surfaceand sealingly engage bore 19 to prevent leakage into a narrow annulus 77defined by seat protector 71 and bore 19. Seat protector 71 must beremoved prior to installing casing hanger 26 and casing string 25.

[0022] In operation, outer wellhead housing 11 and conductor pipe 15 areinstalled, then inner wellhead housing 17, seat protector 71, and outercasing 21 are installed within bore 13 of outer wellhead housing 11.Drilling continues until the proper depth is reached, then seatprotector 71 is removed from within bore 19. Inner casing 25 is loweredinto bore 19 of inner wellhead housing 17, and conduit 67 may beinstalled and lowered into the well along casing 25. Once casing hanger26 lands, shoulders 23, 27 mate, and passages 33, 57 align. Cement ispumped downward through bore 29 of casing 25 to flow up annulus 31.Casing hanger seals 61 are installed. A string of tubing (not shown)will be installed for producing well fluids.

[0023] Pressure in casing annulus 31 can be monitored through passage35. If pressure begins to build up in casing annulus 31, a heavy fluidis circulated through annulus 31. FIG. 1 shows the direction of fluidflow during annulus remediation. Valve 53 is opened to allow thepressure of the heavy fluid in conduit 67 to increase to a level whichovercomes resistance from check valve 69. Fluid passes through passage33 and passage 57 and through conduit 67 to be injected downhole. Valve55 is opened to allow fluid displaced by the injection of the heavyfluid to move up annulus 31, through passage 35, and out of valve 55.

[0024]FIG. 2 shows the direction of fluid flow during cuttingsinjection. The cuttings may be from this well, or may be from anadjacent well being drilled. The injection of cuttings occurs only aftercasing 25 is installed. Valve 55 is opened to allow the slurry ofcuttings to flow through passage 35 and into annulus 31. Cuttings traveldown annulus 31 until reaching the end of outer casing 21 and then flowinto porous formation 32 surrounding casing 25. Cuttings injection wouldnot occur simultaneously with casing annulus remediation.

[0025] Using the present invention has the advantage of providingsystems for both annulus remediation and cuttings injection in the sameassembly. As fluid is displaced by heavy fluids during remediation, thecuttings injection valve provides a controlled exit path for thedisplaced fluids.

[0026] While the invention has been shown in only one of its forms, itis not thus limited but is susceptible to various changes andmodifications without departing from the spirit thereof.

I claim:
 1. A subsea wellhead assembly, comprising: an outer wellheadhousing; an inner wellhead housing; at least one casing hanger landed inthe inner wellhead housing and sealed by a packoff; a passage extendingdownward through a sidewall of the inner wellhead housing from an upperopening on an exterior of the inner wellhead housing to a lower openingin an interior of the inner wellhead housing, the upper opening beingabove the outer wellhead housing, the lower opening being below thepackoff.
 2. The assembly of claim 1, wherein: the lower opening of thepassage is on an interior of the sidewall of the inner wellhead housing.3. The assembly of claim 1, further comprising: a second passageextending downward through the sidewall of the inner wellhead housingfrom an upper opening on an exterior of the inner wellhead housing to alower opening in the interior of the inner wellhead housing, the upperopening of the second passage being above the outer wellhead housing,the lower opening of the second passage being below the packoff.
 4. Theassembly of claim 3, wherein: a conduit extends downward from the loweropening of the second passage, the conduit communicating to a desireddepth a fluid being pumped down the second passage.
 5. The assembly ofclaim 3, wherein: a portion of the second passage passes through thecasing hanger, the lower opening of the second passage being located onan exterior portion of the casing hanger.
 6. The assembly of claim 5,wherein: the packoff comprises upper and lower portions axially spacedapart from each other, the second passage extending between the upperand lower portions.
 7. The assembly of claim 1, wherein: thefirst-mentioned passage is capable of bi-directional fluid flow.
 8. Theassembly of claim 3, further comprising: a retrievable seat protectorlocated in a bore of the inner wellhead housing and covering the loweropening of the second passage prior to the casing hanger being landed.9. In a subsea wellhead assembly having an outer wellhead housingconnected to a string of conductor pipe, forming an outer wellheadassembly, an inner wellhead housing which lands in the outer wellheadhousing and is connected to a first string of casing, forming an innerwellhead assembly, a casing hanger which lands on an internal landingshoulder in the inner wellhead housing and is connected to a secondstring of casing, the improvement comprising in combination: first andsecond passages in the inner wellhead assembly, each passage having anupper opening at an outer surface of the inner wellhead housing and alower opening at an inner surface of the inner wellhead housing, thelower opening of the first passage being located below the landingshoulder and in communication with the annulus, the lower opening of thesecond passage being located above the landing shoulder; and a casinghanger passage in the casing hanger, the casing hanger passage having anupper opening at an outer surface of the casing hanger and above thelanding shoulder, the casing hanger passage also having a lower openingat an outer surface of the casing hanger and below the landing shoulder;and a conduit extending alongside the casing from the lower opening ofthe casing hanger passage for delivering a fluid into a lower portion ofthe annulus; and wherein the lower opening of the second passage and theupper opening of the casing hanger passage are in communication witheach other.
 10. The wellhead assembly of claim 9, further comprising: asealed interface located between the inner surface of the inner wellheadhousing and the outer surface of the casing hanger, the seal defining asealed passage between the lower opening of the second passage and theupper opening of the casing hanger passage.
 11. The wellhead assembly ofclaim 9, further comprising: a valve assembly located at each upperopening of the first and second passages for controlling fluid flowthrough the passages.
 12. The wellhead assembly of claim 9, furthercomprising: a packoff located between the casing hanger passage and theinner wellhead housing above the landing shoulder, the packoff havingupper and lower seal portions axially spaced apart from each other,defining a sealed passage that communicates the lower opening of thesecond passage with the casing hanger passage.
 13. The wellhead assemblyof claim 9, further comprising: a retrievable seat protector located ina bore of the inner wellhead housing and covering the lower opening ofthe second passage prior to the casing hanger being landed.
 14. A methodof injecting a fluid and a volume of cuttings into an annulus of a well,the method comprising; (a) providing a wellhead assembly having a stringof casing defining a casing annulus, first and second passages leadingfrom an exterior portion of the wellhead assembly to the annulus, and aconduit extending downward in the annulus to a selected depth, theconduit having an upper end in communication with the second passage;(b) flowing the fluid downward through the second passage, through theconduit, and into the annulus, the fluid displacing existing fluids inthe annulus, the existing fluids flowing upward and out of the annuusthrough the first passage; and (c) while step (b) is not occurring,flowing a fluid containing the cuttings downward through the firstpassage and into the annulus.
 15. A method of injecting a fluid andoffshore well drilling cuttings into an annulus of a well, the methodcomprising; (a) installing an outer wellhead housing at a subsea floor,the outer wellhead housing being connected to a string of conductor pipethat extends into the well; (b) landing an inner wellhead housing in theouter wellhead housing, the inner wellhead housing having first andsecond passages therethrough, each passage having an upper opening at anouter surface of the inner wellhead housing and a lower opening on aninner surface of the inner wellhead housing, the lower opening of thefirst passage being located below an internal shoulder, the loweropening of the second passage being located above the internal shoulder;(c) securing a string of casing to a casing hanger and landing thecasing hanger on the internal shoulder, the casing hanger having apassage sealingly communicating the lower opening of the second passageand a conduit extending alongside the casing in an annulus; (d) pumpinga fluid into the annulus through the second passage, with existing fluidlocated in the annulus being forced out of the annulus through the firstpassage; and (e) while step (d) is not occurring, pumping cuttings intothe annulus through the first passage.
 16. The method of claim 15,further comprising: after step (b) and before step (c), inserting a seatprotector within the bore of the inner wellhead housing to preventcontact with the lower opening of the second passage during drilling.